Conventionally, there have been known, for example, electric vehicles, for which a drive force generated by a rotary electric machine, such as a motor generator, is employed to drive the vehicles, hybrid vehicles that combine a rotary electric machine with an engine that is an internal combustion engine, and fuel cell vehicles, for which electric power generated by a fuel cell is employed to drive the vehicles. These vehicles are equipped with a PCU (Power Control Unit) that includes a boost converter and an inverter for receiving electric power supplied by a battery and for controlling the transmission of electric power to a motor generator (hereinafter referred to also as a motor). It should be noted that the power control unit is also called a PCU.
Generally, supply of a high voltage is required for efficient operation of a motor, and, for example, a hybrid vehicle is well known, on which a boost converter that increases a battery voltage from about 200 V to about 600 V is mounted. The boost converter includes switching elements and a reactor connected to the switching elements, and the reactor includes a core, such as an icon core, made of a magnetic material, and a coil provided for the core. Further, when the boost converter controls the ON/OFF states of the switching elements, the reactor is permitted to accumulate or discharge the electric power, and a voltage supplied from the battery can be increased, and the increased voltage can be supplied to the inverter. At this time, the core of the reactor generates heat in association with electromagnetic energy conversion, and the coil is heated by the Joule heat of a conductive current. In a case wherein heat dissipation is not appropriately performed, a rise in the temperature of the reactor would occur, and the voltage conversion efficiency for the boost converter would be reduced, and therefore, appropriate dissipation of heat from the reactor is required. Thus, as for heat release from the reactor, there are heat dissipation techniques; for example, using a cooling fin provided for the reactor, and using a liquid coolant.
In patent document 1, a drive unit for a hybrid vehicle, which is equipped with a boost converter that employs a reactor as a constituent, is disclosed. According to the drive unit described in patent document 1, when an inverter and a motor are arranged together in a single case, lubricating oil pumped up by rotation of a motor generator is introduced into a housing chamber where a reactor is housed, and the lubricating oil thus accumulated in the housing chamber is employed to cool the reactor in order to encourage heat dissipation from the reactor.
A conventional drive unit 100 is shown in FIG. 8, and a motor generator MG2 and a reactor L1 in cross section are shown in front, while a capacitor C2, a cooler 108, a power element board 109, and a motor generator MG1 are shown behind the motor generator MG2 and the reactor L1. In accordance with rotation of the motor generator MG, lubricating oil is pumped up, as indicated by arrows F2 and F2, and is passed through a housing chamber opening 340 and is introduced into a reactor housing chamber 300. The thus introduced lubricating oil cools the reactor L1, and is discharged from an oil drain hole 320 to an opening 102, as indicated by F3. With this arrangement, the coolability of the reactor L1 can be obtained.